Electric alarm clock



I v Jan. 14, 1936. L, HAMMOND ELECTRIC ALARM CLOCK Filed Feb. 13, 19311 Jn/gr.-

Patented Jan. 14, 1936 UNITED STATES PATENT OFFICE ELECTRIC ALARM cLoox Application February 13, 1931, Serial No. 515,600

2 Claims.

My invention relates generally to electrically operated alarm clocks, and more particularly to improved means for setting and operating the alarm mechanism in this typ'e of clock.

It is an object of my invention to provide alarm buzzer means operable by the field coil of the electric motor.

A further object is to provide a device of this type in which the sounding member is held out of the denser portion of the magnetic field of the electric motor during normal operation and permitted to move into the denser field lwhen it is to be rendered operative to sound the alarm.

, A further object is to provide an electric alarm l5 clock in which the necessity for electrical contacts, auxiliary springs, etc., is entirely eliminated.

A further object is to provide an electric alarm clock which is extremely simple in construction, positive in operation, and may be economically 80 manufactured.

Other objects will appear from the following description, reference being had to the accompanying drawing, in which Figure 1 is a fragmentary elevation of portions 95 of an electric clock and alarm mechanism;

Figure 2 isa vertical sectional View taken on the line 2-2 of Fig. 1;

Figure 3 is a fragmentary detailed elevational view taken on the line 3-3 of Fig. l;

Figure 4 is a rear elevation of the setting knob taken on the line 4-4 of Fig. 2; and

Figure 5 is a diagrammatic view of the clock gear train and alarm mechanism.

My invention may be applied to many different types of clocks operating on analternating current supply but is particularly adapted for use in connection with synchronous motor driven clocks of the general ltype disclosed in my United States Letters Patent No. 1,719,805, granted July 2, 1929, or in conjunction with clocks utilizing a synchronous brake escapement mechanism of the type shown in my copcnding applications Serial Nos. 515,598 and 515,599, filed February 13,

As fully disclosed in the aforesaid applications for letters Patent, a rotor I8 having field poles I2 and I4 forms a synchronous brake accurately to control the speed of operation of the clock in accordance with the frequency of the current supo plied. The poles I2 and I4 are preferably lam'inated, and are secured together with bars I6 by means of bolts I8 and 20. Acoil 22 is wound about v the inwardly projecting ends of the eld pieces I2 and I4 and about the bars I6. A soft iron angle 55 clip 24 ls secured to the core of the coil, having a horizontally projecting upper portion. A similar clip 26 is secured to the core at the other side of the coil by the bolt 20, this clip having a horizontally projecting portion 28 to which a spring finger 30 is rigidly secured. The spring finger is preferably i madev of brass or other non-magnetic material. A clapper plate 32 of magnetic material is adapted to bridge the space between the projection 28 and the horizontal portion of the clip 24, the plate v being secured to an arm 34 pivoted on a shaft 36. lo A spring 38 is tensioned to draw the clapper plate against the spring 30, the latter spring being the stronger and being capable of holding the parts in the position shown in Fig. l against the tension of the spring 38. 15 The arm 34 is preferably formed integrally with a sleeve 48 which has a cam follower arm 42 formed integrally therewith. The follower cooperates with a cam disc 44 which is rigidly secured to a sleeve 46, the latter being rotatably 20 mounted upon a shaft 48 but normally moving therewith because of the friction exerted by the right-hand end of the sleeve (Fig. 2) against a friction washer 50. The washer is held against an indicator hand 52 secured to the end of the 25 shaft 48. The sleeve 46 is normally pressed against the washer by a coil spring 54 compressed between the hub of a gear 56 and the hub of the cam 44. The cam 44 has a notch 58 formed therein, which, when in alinement with the end 30 of the follower arm 42, permits the latter to swing counterclockwse as shown in Fig. 1. The sleeve 40 has an arm 68 secured thereto or formed integrally therewith, the arm being adapted to be engaged by a lever 62 (Fig. 3) which is friction- 35 ally secured to a leg 64 rigid with the frame of the clock, and projects outwardly through the rear casing thereof so as to be manually shiftable y through an arc as indicated in Fig. 3 by the full and dotted line positions, the friction in the piv- 40 otal mounting of the lever 62 being suicient to overcome the force of the coil spring 38.

The gear 56 is driven from the hour hand gear 66 of the clock gear train through idlers 68, 'l0 and 1 I so that the gear 56 will make one revolu- 45 tion in twelve hours. The speed of rotation of the gear 66 is controlled by the speed of revolution of the rotor I0, being connected thereto by suitable train of gearing as illustrated in Fig. 5.

A drum 12 is rigidly secured to the end of the 50 sleeve 46 and, as shown in Fig. 4, has suitable indicia thereon to cooperate with the pointer 52 in indicating the timeat which it is desired to have the alarm sound. The outer edge of this drum is preferably knurled, facilitating manual rotation thereof. As indicated in Figs. 1 and 2, the gear 66 is secured to a sleeve 14 which projects through the dial 16 of the clock, and at its end carries an hour hand 18. The gearing for driving the minute hand 88 and second hand 82 is not shown and may be of any well known suitable construction.

In operation, the user will rotate the drum 'l2 until the pointer 52 indicates the time at which he wishes the alarm to sound, thereby rotating the cam 44 and setting the position of the latter with respect to the gear 56. After having-been set, the spring 54 will press the sleeve 46 against the friction washer with sufficient force that thereafter there will not be any relative movement between the gear 56 and the cam 44. 'I'he cam will thus be driven at the rate o,f one revolution in twelve hours from the gear 66 through the idler gears 68, 10 and 1l. When the cam has rotated to the position illustrated in Fig. 1., the follower 42 will drop into the notch 58 under the iniiuence of the spring 38, vand the clapper plate 32 thus drawn to a position closely adjacent toy the projection 28 and the horizontal portion of the clip 24, in which position it will be inuenced by the varying magnetic flux generated by the coil 22 and continue vibrating at twice the frequency of the alternating current supplied tothe coil 22.

When the alarm is thus sounding, the clapper. plate 32 will form a magnetic flux bridge between the clip 24 and the projection 28, andwill be .drawn toward said elements when the ux is at its maximum density. As the intensity of the flux decreases, the spring nger 30 will force the clapper plate away from the clip 26 and projection 28, this operation being repeated at a frequency equal to twice that of the frequency of the alternating current supplied to the coil. The spring finger 36 prevents the clapper plate from sticking to the clip 26 and projection 28. 'I'he user may readily shut off the alarm by swinging the lever 62 downwardly, thereby swinging the 5 clapper plate 32 a suicient distance from the clip 26 and projection 28 that it will not be materially affected by the variations in flux density generated by the coil 22. V

While I have illustrated and described a prel0 ferred embodiment of my invention, many modi- I cations may be made without departing from the spirit of the invention, and I do not wishto be limited to the precise details set forth but desire to avail myself of all changes within the scope l5 of the appended claims.

' 1.In an electric clock, the combination of a.

.time gear train, a shaft driven thereby, a cam connected to said shaft so as normally to rotate therewith, a manually engageable indicator se- 20 cured to said cam and positioned at the back of the clock, a pointer on said shaft and cooperable with said indicator, said pointer being independent of the hands of the clock, and an' alarm mechanism controlled by said carn.

2. In an alarm clock, the combination of a time gear traima shaft driven thereby, a cam frictionally connected'to said shaft so as normally to rotate therewith, a manually engageable indicator secured to saidl cam and positioned at the 30 back of the clock, a pointer on said shaft and cooperable with said indicator, and an alarm mechanism comprising a member adapted to be moved into and out of a magnetic eld by said cam and to sound an alarm when it is in said field, said 35 alarm mechanism being controlled by said cam.

LAURENS HAMMOND. 

